JP3154717B2 - Method for producing electrophotographic lithographic printing plate by reversal development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a method for producing an electrophotographic lithographic printing plate by reversal development, in which image information output from an electronic editing system or the like is directly written on an organic semiconductor and subjected to reversal development to obtain a printing plate.

[Prior art]

Many methods for preparing a lithographic printing plate are already known. For example, the original is closely adhered to the printing plate with a silver halide film,
The photosensitive layer of the original is directly exposed to ultraviolet light or the like, thereby forming a cured portion corresponding to the image portion of the document and a non-cured portion corresponding to the non-image portion, and washing and removing the non-cured portion with an alkali or water. This is a plate making method in which a cured portion is made ink-receptive. The printing plate obtained by this method is called a so-called PS plate, and is widely used. On the other hand, due to advances in computer image processing technology, memory development of large-capacity data, and data communication technology, in recent years, computer operation has been consistently performed from document input, correction, editing, layout, and page set, and high-speed communication networks and satellite communication As a result, an electronic editing system that can immediately output to a remote terminal plotter has been put to practical use. In particular, not only electronic editing systems but also plate making systems in which printing plates are directly obtained from data therefrom are being put into practical use in the newspaper printing field and the like, where immediacy is required. At present, in such a plate making system, a system using an electrophotographic process and exposing with a laser light source (semiconductor laser, He-Ne laser, etc.) is expected from various aspects. Further, in such a system, the following elution-type electrophotographic lithographic printing plates can be advantageously used because they can be printed under the same printing conditions as the conventionally used PS plates. . The main plate-making process involves charging, exposing, and developing the printing original plate, forming an image with toner, removing the non-image area where toner does not adhere with an eluent, and subjecting the support surface to hydrophilic treatment in advance. To make a printing plate. Here, since the image area protected by the toner is lipophilic, offset printing can be performed. An electrophotographic lithographic printing plate is produced from an electrophotographic photosensitive member in which a photoconductive layer containing a photoconductive substance is adhered on a conductive support such as aluminum. The material constituting the photoconductor layer of the electrophotographic photosensitive member is described in JP-B-37-17162.
No. 38-7758, No. 46-39405, JP-A-52-2437
No. 57-161863, No. 58-2854, No. 58-28760,
Nos. 58-118658, 59-12452, 59-49555, 62
Organic photoconductive compound / binder resin materials as described in JP-A-217256, JP-A-63-226668 and JP-A-1-21659 are excellent in practical sensitivity, printing durability and the like. In the process of making an electrophotographic lithographic printing plate, a predetermined charging process is first performed on the photoconductor layer of the electrophotographic photoreceptor, and a uniform charge is applied. Next, an electrostatic latent image corresponding to the image is formed by exposure. Subsequently, development and fixing using an electrophotographic developer are performed, and a toner image corresponding to the electrostatic latent image is formed. The non-image area other than the toner image is dissolved and removed (eluted) by a solution containing an alkaline agent or the like, and then the apparent pH of the plate surface is adjusted by washing with water or an acidic rinsing liquid, and if necessary, Processing such as application of a plate surface protection liquid (protective gum liquid) is performed to obtain a final printing plate. By the way, in the development process, if a toner image is obtained by so-called reversal development, a good image free from fog and line thinning can be obtained from its development characteristics. Recently, particularly high resolution and high quality image reproducibility are required, and a method for producing an electrophotographic lithographic printing plate by reversal development is a method that meets this quality requirement. In the case of performing reversal development, first, light irradiation is performed on a portion (image portion) where toner is to be attached in the exposure process, and the potential of the light irradiated portion is attenuated to approximately 0V. At this time, a portion where light irradiation is not performed (a portion corresponding to a non-image portion) maintains the initial charging potential as it is.
A predetermined developing bias is applied to the developing process region via an electrode, and a predetermined developing electric field is formed by the developing bias. On the other hand, the toner particles in the developer have a charge of the same polarity as that of the photoconductor charged by a predetermined method. In such a state, when a photoconductor having an electrostatic latent image is carried in the developing electric field in the developing process area, the toner particles in the developer are transferred to the photoconductor by the developing electric field, and the light-irradiated portion is formed. The toner particles adhere to the 0 V portion of the photoconductor. At this time, the portion corresponding to the non-image portion where the initial charge potential remains remains repelled by the toner particles, so that adhesion of the toner particles is avoided. As a developer used for such reversal development, generally, both a dry developer developer and a liquid developer can be adopted. However, according to the liquid developer, toner particles can be made finer. Therefore, good image reproducibility with high resolution can be obtained. The liquid developer is obtained by dispersing a pigment (dye) or a polymer particle in a highly insulating medium to perform coloring, and adding a charge (charge) controlling agent thereto to give a predetermined charge. Here, the amount of adhered toner, that is, the image density in the development process is determined by various image forming conditions, but the amount of charge of the toner particles is extremely important in determining image quality such as image density. Conditions.
That is, as described above, in the reversal development, a zero potential portion is formed in the initial uniformly charged area on the photoreceptor side by exposure, and the zero potential portion is filled with the charge of the toner particles so that the toner adheres. Is performed. For this reason, the amount of toner attached varies depending on the amount of charge of each toner particle. Generally, when the amount of charge of each toner particle is large, the amount of attached toner particles decreases and the image density decreases,
When the charge amount of each toner particle is small, the amount of toner particles attached increases, and the image density increases.

[Problems to be solved by the invention]

On the other hand, the charge amount of the toner particles is not limited to changing the image density as described above, but causes the following development. First, let us consider a case where a non-image portion in which the initial charge potential remains as it is is continuously fed into the original stroke area. In this case, when the developing bias potential applied from the opposing electrode plate is lower than the charging potential, the toner particles charged to the same polarity as the charging potential of the non-image portion receive a repulsive force from the non-image portion. And is pushed back to the counter electrode plate side. Therefore, when the non-image portion is continuous, the toner particles are electrodeposited on the surface of the counter electrode plate and accumulate, or the state in which the toner particles are localized on the counter electrode plate side becomes gradually remarkable. Go. On the other hand, a new electric field may be generated from the toner particles deposited or accumulated on the counter electrode plate side or in a densely localized state. The electric field generated from these toner particles is applied to the bias voltage as an additional electric field in addition to the original developing bias electric field. When the additional electric field increases, a predetermined amount of toner particles may suddenly start to move toward the photoconductor at a certain timing. This phenomenon occurs regardless of the non-image portion and the image portion, and causes a large amount of toner adhesion. The present inventors named such a phenomenon a toner avalanche phenomenon. If the toner avalanche phenomenon described above occurs in the development process of an electrophotographic lithographic printing plate, toner adheres to non-image areas other than the desired image, preventing elution of the non-image areas, and as a result, this phenomenon When printing is performed using an electrophotographic lithographic printing plate in which blemishes have occurred, the resolution of the printed matter is reduced, and printing stains are caused. Thus, the toner avalanche phenomenon significantly lowers the quality of the printing plate. Accordingly, it is an object of the present invention to provide a method for producing an electrophotographic lithographic printing plate by reversal development which enables a toner image to be favorably obtained without causing a toner avalanche phenomenon.

[Means for solving the problems]

In order to achieve the above object, the present invention provides a method for uniformly charging the surface of an organic photoconductor formed by binding an organic photoconductive compound on a conductive support with a resin material, exposing a light image, Forming an electrostatic latent image on the surface of the organic photoreceptor, and then reversely developing the electrostatic latent image using an electrophotographic liquid developer containing charged toner particles to produce a printing plate. In the method for producing an electrophotographic lithographic printing plate by reversal development, the electrodeposition potential as a liquid developer is 0 to 80 as an absolute value.
The configuration is such that reversal development is performed using an electrophotographic liquid developer set within the range of V. In the present invention, since the electrodeposition potential as the electrophotographic liquid developer is kept within a predetermined range, that is, within the range of 0 to 80 V as an absolute value, occurrence of toner avalanche development is avoided and proper liquid reversal is performed. Development can be carried out, and a good printing plate having excellent resolution can be produced. The configuration of the present invention will be described more specifically. First, as the electrophotographic liquid developer used in the present invention, a pigment such as carbon black is dispersed in a highly insulating hydrocarbon medium together with a dispersing resin, or a pigment is colored with a dye instead of a pigment, and a charge controlling agent is used. There is a dispersion of colored resin particles charged by a high-insulating hydrocarbon medium,
It can be applied to any of them. A liquid developer of a resin particle dispersion type is excellent in dispersion stability, charge stability and fixability. The highly insulating hydrocarbon medium used in the present invention is an organic solvent having a low dielectric constant and a high electric insulating property, for example, n-paraffinic hydrocarbon, isoparaffinic hydrocarbon, alicyclic hydrocarbon, aromatic Hydrocarbons, halogenated aliphatic hydrocarbons and the like can be mentioned, and isoparaffinic hydrocarbons are preferably used. For example, Shell Sol 71 (made by Shell Petroleum), Isopar G and Isopar H, Isopar K and Isopar L (made by Esso Petroleum) ), IP solvent (made by Idemitsu Petroleum), etc. are used. JP-A-59-83174, JP-A-59-177572, JP-A-59-212850, JP-A-59-212851, and JP-A-60-83174
No. 164757, No. 60-179951, No. 60-185962, As described in No. 60-185963, in the presence of a polymer soluble in a highly insulating medium by a so-called dispersion polymerization method. In this method, a monomer which is soluble in the solvent but becomes insoluble when a polymer is formed is polymerized, and the obtained resin dispersion is used as a liquid developer. Furthermore, Japanese Patent Laid-Open No. 62
Liquid developers described in JP-A-231266, JP-A-62-231267, JP-A-62-232660, JP-A-63-178258, and JP-A-63-179368 can also be suitably used. The liquid developer is excellent in stability in industrial production, dispersion stability, and the like. As the colorant for the dispersed resin particles of the liquid developer used in the present invention, those generally known as wet developer colorants can be arbitrarily used. For example, oil black,
Oil-soluble dyes such as oil red, basic azo dyes such as bismarck brown and chrysoidin, acidic azo dyes such as wool black, amide black green and blue black HF, direct dyes such as direct day black E and congo red, sudan vilet , Anthraquinone dyes such as Acid Blue, auramine, malachite green,
Dyes such as crystal violet, carbonium dyes such as Victoria Blue, rhodamine dyes such as Rhodan B, and quinone imine dyes such as safranine, nigrosine, and methylene blue. As a method of coloring the dispersed resin particles, there is a method of dissolving the coloring agent to be used in advance in a solvent that dissolves the coloring agent, and then dropping and stirring the colorant solution to the dispersed resin particle liquid. In particular, coloring can be preferably performed by dissolving an oil dye in an aromatic solvent such as toluene or xylene and performing dropwise stirring. At this time, it is desirable that the solvent for dissolving the colorant is mixed with, for example, an isoparaffinic hydrocarbon solvent used as the medium. Furthermore, it is desirable to use a solvent that dissolves the dye, which has relatively insulating properties and a high boiling point.For example, when an oil-soluble dye is used, if an aromatic hydrocarbon is used, a small amount of xylene or the like is used. Even if the solvent is not removed, a liquid developer which can sufficiently be used as an electrophotographic liquid developer can be manufactured.
Therefore, when using a dye using a dye having a relatively high solubility in an organic solvent such as an oil-soluble dye, if the amount of the solvent that dissolves the dye is reduced, the above-mentioned solvent is used after coloring the dispersed resin particles. There is no need to remove it. As the liquid developer used in the present invention, if a charge control agent, a dye and the like are selected, a toner having a positive charge property or a negative charge property can be manufactured. Examples of the charge control agent of the liquid developer used in the present invention include copper oleate, cobalt naphthenate, zinc naphthenate, aluminum stearate, manganese naphthenate, cobalt octylate, lecithin, sodium dioctyl sulfosuccinate, and stevelite. Aluminum salts of rosin, etc.
JP-A-49-26595, JP-A-60-173558, JP-A-60-175060, JP-A-60-179750, and JP-A-60-
No. 182447, No. 60-218662, No. 61-278867, No. 62-30260, No. 62-34170, No. 63-12
The charge control agents listed in 4056 and the like can be used. To produce a toner having negative charge, a monomer having a base soluble in the medium (eg, a copolymer of lauryl methacrylate and dimethylaminoethyl methacrylate), pyromellitic acid, trimellitic acid, trimesin An acid insoluble in the medium such as an acid or benzoic acid can be used in combination, but is not limited to these. The measuring device for obtaining the electrodeposition potential according to the present invention includes, for example, a glass cell having a main electrode and a counter electrode, a high voltage applying device, a surface potential measuring device, and the like. As a measuring method, a liquid developer to be measured is put into a glass cell equipped with an electrode, a high voltage applying device is connected to the electrode, and after applying a voltage for a certain time, the main electrode on which the toner is electrodeposited is pulled up and a surface voltmeter is used. Measure the potential on the electrode surface. At this time, the distance between the electrodes, the applied voltage, the applied time, and the like can be arbitrarily set. However, it is preferable to set the distance close to the actual state of development. Further, the measuring method of the present invention can measure whether the polarity of the charge of the toner particles in the liquid developer is positive or negative as long as the polarity of the main electrode is adapted to it. The standard evaluation method of the present invention is defined below. Put two flat electrodes in a liquid developer and apply an electric field of 30,000 V / m
Immediately after the application, the electrode plate is gently pulled out of the liquid developer, and the potential generated from the toner electrodeposited on the electrode is measured with a surface voltmeter. The electrophotographic lithographic printing plate used in the present invention has at least one or more photoconductive layers on a conductive support. As the conductive support, a plastic sheet or paper having a conductive surface, or an aluminum plate, a metal plate such as a zinc plate or the like is used, and the thickness thereof is preferably 0.1 to 3 mm, particularly preferably 0.1 to 0.5 mm. . Among these substrates, an aluminum plate which is roughened and has an anodic oxide film is preferable. Further, the aluminum plate applied to the present invention is not limited in its composition, surface treatment and the like, and any conventionally known and publicly available printing plate material can be appropriately used. A conventionally known electrophotographic photosensitive layer is provided on such a conductive support. Many conventionally known inorganic or organic compounds can be used as the photoconductive material used for the electrophotographic photosensitive layer. For example, inorganic photoconductive materials include selenium and selenium alloys, amorphous silicon, Cd, CdSe, CdSSe, ZnO, ZnS, and the like. Further, as the organic photoconductive material, known organic photoconductive compounds such as phthalocyanine and derivatives thereof can be used. Organic photoconductive compounds are
If desired, two or more kinds can be used in combination. In addition, various pigments, dyes, and the like can be used in combination for the purpose of improving the sensitivity of the photoconductor and giving sensitivity to a desired wavelength region. In photoreceptors for electrophotographic printing plates, the photoconductive compound itself may have film properties, but if the photoconductive compound alone does not have film properties, a binder resin may be used in combination. I can do it. In the electrophotographic photoconductive layer, it is necessary to finally remove the non-image part photoconductive layer. This step is based on the relative relationship between the solubility of the photoconductive layer in the eluate and the resistability of the toner image in the eluate. However, at least the binder resin is preferably a polymer compound soluble or dispersible in an eluate described later. A monomer-containing copolymer having an acid anhydride group or a carboxylic acid group and a phenol resin have a high charge retention when used as a photoreceptor for an electrophotographic printing plate, and can therefore be advantageously used. As a monomer-containing copolymer having an acid anhydride group,
A copolymer of styrene and maleic anhydride is preferred. Examples of the monomer-containing copolymer having a carboxylic acid group include a copolymer of styrene and maleic acid monoester, and a copolymer of acrylic acid or methacrylic acid and their alkyl ester, aryl ester or aralkyl ester. Coalescence is preferred. Further, a copolymer of vinyl acetate and crotonic acid is also good. Particularly preferred phenolic resins include novolak resins obtained by condensing phenol, o-cresol, m-cresol, or p-cresol with methanal or ethanal under acidic conditions. The binder resin may be used alone or in combination of two or more. The electrophotographic lithographic printing plate used in the present invention is obtained by coating a photoconductive layer on a conductive support according to a conventional method. In producing the photoconductive layer, a method of including the components constituting the photoconductive layer in the same layer, or a method of separately including two or more layers, for example, a charge carrier generating material and a charge carrier transporting material. A method of separating and using different layers is known, and any method can be used. The coating solution is prepared by dissolving each component constituting the photoconductive layer in an appropriate solvent, but when using a component insoluble in a solvent such as a pigment,
It is used by dispersing with an average particle size of 0.01 to 5 μm using a dispersing machine such as a ball mill, a paint shaker, and a dyno mill. The binder resin and other additives used in the photoconductive layer can be added during or after the dispersion of the pigment or the like. An electrophotographic lithographic printing plate can be obtained by applying the coating solution thus prepared on a support by a known method such as spin coating, blade coating, dip coating, rod bar coating, spray coating and the like. If necessary, in addition to the photoconductive compound and the binder resin, a plasticizer, a surfactant, and other additives may be added to the photoconductive layer for the purpose of improving the film properties such as the flexibility of the photoconductive layer and the shape of the coated surface. Can be added. An intermediate layer may be provided between the conductive support and the photoconductive layer, if necessary, to improve adhesion, electrophotographic properties, and the like. The electrophotographic lithographic printing plate thus prepared is cut into a desired size, and is used as a printing plate by the following plate making method. In order to prevent ink stains caused by the side portions of the electrophotographic lithographic printing plate, a layer for holding a potential in the charging step may be provided on the side portions of the cut electrophotographic lithographic printing plate. Further, in order to promote elution of the layer, an intermediate layer or the like having higher hydrophilicity than the potential holding layer can be provided below the potential holding layer.

【Example】

Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to the toner particle synthesizing method and the examples of the liquid developer shown here, and the liquid developer having an electrodeposition potential in the range of 0 to 80 V Plate making is the gist of the present invention. Example 1 (Synthesis example of emulsion) A 40% xylene solution of n-hexyl methacrylate-methacrylic acid copolymer (weight ratio 95/5) was obtained by a known solution polymerization method. When 30 g of this solution was added to 1 L of hexane, a precipitate of the copolymer was obtained as a slurry. It washed several times decantation slurry in hexane, with N ₂ gas inlet tube, a thermometer, a stirrer, a cooling tube 1L
And a 450 g IP solvent (made by Idemitsu Petrochemical Co.) was added. Next, 130 g of vinyl acetate and 30 g of lauryl methacrylate were added and stirred well to obtain a uniform transparent solution. 80
After purging with N ₂ gas at ° C., 1 g of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and the polymerization started. After about 40 minutes, the solution became cloudy and the internal temperature rose to 110 ° C.
After the internal temperature dropped to 80 ° C., heating was further applied for 2 hours. In order to remove the remaining vinyl acetate monomer, the inside was distilled off under reduced pressure to obtain about 3 g of a distillate. The resulting white emulsion had no precipitate and almost no monomer odor. When the particle size was measured with an electron microscope, it was found that the particle size was 0.20 μm and there was almost no particle size distribution. (Production Example of Positively Chargeable Liquid Developer) In 70 g of the emulsion obtained in the above synthesis example, 2 g of oil black HBB (manufactured by Orient Chemical Co., Ltd.) dissolved in 20 g of xylene was dropped while being irradiated with ultrasonic waves. The emulsion particles were colored. Then, as a charge control agent, 1%
A xylene solution of an Al salt, 0.3 g, 0.6 g, 1.2 g, 3 g, and 6 g were respectively added to obtain five types of conc (concentrated) toners. Each of these conk toners is a total of 10 with Isopar G.
It was diluted to L to obtain a positively charged liquid developer. (Measurement of Electrodeposition Potential) An electrode 12 and a counter electrode 13 were placed in the glass cell 11 shown in FIG.
Installed so that a gap of 2 mm can be obtained, gently inject 7 cc of liquid developer, and use a high voltage supply device 14 (ADVANTEST TR3
When a voltage of 600 V was applied between the electrodes 12 and 13 for 10 seconds from 00C), toner particles were electrodeposited on the electrodes 12. Immediately thereafter, the electrode 12 (-pole) is gently pulled up, and the surface potential near the center of the adhered toner is measured using a surface potentiometer 15 (MODEL manufactured by TREK).
362A). The electrodeposition potentials of the positively-chargeable liquid developers A, B, C, D, and E prepared as described above were as shown in Table 1. A JIS1050 aluminum sheet was immersed in a 10% NaOH aqueous solution at 60 ° C., and was etched so that the amount of aluminum dissolved was 6 g / m ² . After washing with water, it was immersed in a 30% nitric acid aqueous solution for 1 minute to neutralize, and sufficiently washed with water. Thereafter, electrolytic surface roughening was performed in a 0.7% aqueous nitric acid solution for 20 seconds, and the surface was washed by immersion in a 20% aqueous sulfuric acid solution at 50 ° C., followed by washing with water. In addition, 20%
An anodizing treatment was carried out in an aqueous sulfuric acid solution, followed by washing with water and drying to prepare a printing plate support. The surface of the support is treated with a paint shaker.
The following photoconductive layer composition dispersed in time was applied with a bar coater, and dried at 90 ° C. for 5 minutes to prepare an electrophotographic lithographic printing plate. At this time, the coating amount of the photoconductive phase was 4.5 g / m ² . Composition of coating liquid for photoconductive layer Butyl methacrylate / methacrylic acid copolymer (40% methacrylic acid) 18 parts Metal-free phthalocyanine 4 parts 60 parts butyl acetate 2-propanol 18 parts (reversal development) Master plate for printing prepared in this manner Is charged so that the surface potential (V ₀ ) becomes about +300 V by applying a corona discharge in a dark place, and then subjected to scanning image exposure using a semiconductor laser (780 nm), and immediately above A, B, C, and D , And E, liquid reversal development was performed. The developing bias voltage in this reversal development was set between 0 and + 300V. After the toner development, cold air drying was performed. Next, heat fixing was performed by an infrared lamp to form a toner image on the photoconductive layer. The results of toner development using the five types of liquid developers A, B, C, D and E are as follows. When A to C were used, good and clear images were obtained, and high reproducibility was obtained for both halftone dots and fine lines. When the liquid developers D and E were used, the shadow portions of the halftone dot portions were crushed, and only unsuitable images were obtained.
In particular, in the case where the non-image portion is continuous, the toner particles charged to the same polarity as the non-image portion receive the repulsive force from the non-image portion and move to the electrode plate side, and the toner particles are electrodeposited on the electrode plate surface. Then, the state of accumulation and the state where the toner particles were localized and clogged gradually became remarkable. Since the individual toners in the electrodeposited and accumulated or localized state have a large charge, the electric field generated from the toner particles is added to the original developing electric field. A large amount of toner particles suddenly started to move to the photoreceptor side at a certain timing, and a toner avalanche phenomenon in which a large amount of toner adhered regardless of a non-image portion and an image portion occurred. (Plate making process) Next, a plate making process was performed using an eluate, a washing solution and a rinsing solution as shown below. (1) Eluent composition Sodium silicate aqueous solution (SiO ₂ content 30% by weight, SiO ₂ / Na ₂ O molar ratio 2.5) 20 parts Potassium hydroxide 1 part Pure water 79 parts (2) Rinse solution composition Dioctyl sodium sulfosuccinate 0.1 Part Pure water 99.9 parts (3) Rinse solution composition Citric acid 0.8 part Phosphoric acid (85% aqueous solution) 0.5 part Decaglyceryl monolaurate 0.05 part Pure water 100 parts No failure such as poor elution was observed. When printing was performed in a conventional manner using the five types of printing plates thus obtained, the printing plate obtained according to the present invention provided a printed material having good, clear, high-quality images. Was completed. On the other hand, in the case of using a printing plate outside the present invention, good printed matter could not be obtained. In particular, in a printing plate in which a toner avalanche phenomenon occurred, a shadow portion of a halftone dot was crushed, and only an unsuitable copy was obtained. Example 2 (Production Example of Negatively Chargeable Liquid Developer) The procedure up to coloring of the emulsion particles was performed in exactly the same manner as in Example 1 described above. Trimellitic acid and dimethylaminomethacrylate (20 W%) were used as negatively chargeable charge control agents. And Lauryl methacrylate (80W%) copolymer IP solvent 5
0% solutions were added at the ratios shown in Table 2 to obtain five types of conc (concentrated) toners. Each of these conc toners was diluted to 10 L of total with Isopar G to obtain a negatively chargeable liquid developer. Each of these negatively chargeable liquid developers F,
Table 3 shows the respective electrodeposition potentials of G, H, I and J.
It was like. The measurement of the electrodeposition potential was performed in the same manner as in the above electrodeposition potential measurement method except that the polarity of the electrode of the cell was reversed. (Preparation of an electrophotographic lithographic printing plate) A JIS1050 aluminum sheet was immersed in a 10% aqueous NaOH solution at 60 ° C., and was etched so that the amount of aluminum dissolved was 6 g / m ² . After washing with water, it was immersed in a 30% nitric acid aqueous solution for 1 minute to neutralize, and sufficiently washed with water. Thereafter, electrolytic surface roughening was performed in a 0.7% aqueous nitric acid solution for 20 seconds, and the surface was washed by immersion in a 20% aqueous sulfuric acid solution at 50 ° C., followed by washing with water. In addition, 20%
An anodizing treatment was carried out in an aqueous sulfuric acid solution, followed by washing with water and drying to prepare a printing plate support. The surface of the support is treated with a paint shaker.
The following photoconductive layer composition dispersed in time was applied with a bar coater, and dried at 90 ° C. for 5 minutes to prepare an electrophotographic lithographic printing plate. At this time, the coating amount of the photoconductive layer was 4.5 g / m ² . (Reversal Development) The electrophotographic lithographic printing plate precursor obtained as described above was subjected to corona discharge in a dark place to give a surface potential (V ₀ ) of about −35.
After charging to 0 V, He-Ne laser (633n
m), and scan image exposure using immediately F, G, H,
Liquid reversal development was performed using one of the liquid developers I and J. The developing bias voltage in this reversal development is 0.
Or between -300V. After the toner development, a toner image was formed on the photoconductor layer by cold air drying and heat fixing. The results of toner development using the five types of liquid developers F, G, H, I, and J were as follows. When the liquid developers F to H were used, good and clear images were obtained, and high reproducibility was obtained for both halftone dots and fine lines. When the liquid developers I and J were used, the shadow portion of the halftone dot portion was crushed, and only an unsuitable image was obtained.
In particular, in the case where the non-image portion is continuous, the toner particles charged to the same polarity as the non-image portion receive the repulsive force from the non-image portion and move to the electrode plate side, and the toner particles are electrodeposited on the electrode plate surface. Then, the state of accumulation and the state where the toner particles were localized and clogged gradually became remarkable. Since the individual toners in the electrodeposited and accumulated or localized state have a large charge, the electric field generated from the toner particles is added to the original developing electric field. A large amount of toner particles suddenly started to move to the photoreceptor side at a certain timing, and a toner avalanche phenomenon in which a large amount of toner adhered regardless of a non-image portion and an image portion occurred. (Plate making process) Next, a plate making process was performed using an eluate, a washing solution and a rinsing solution as shown below. (1) Eluent composition Sodium silicate aqueous solution (SiO ₂ content 30% by weight, SiO ₂ / Na ₂ O molar ratio 2.5) 20 parts Potassium hydroxide 1 part Pure water 79 parts (2) Rinse solution composition Dioctyl sodium sulfosuccinate 0.1 Part Pure water 99.9 parts (3) Rinse solution composition Citric acid 0.8 part Phosphoric acid (85% aqueous solution) 0.5 part Decaglyceryl monolaurate 0.05 part Pure water 100 parts No failure such as poor elution was observed. Printing was performed using the five types of printing plates thus obtained. With the printing plates obtained according to the present invention, it was possible to obtain printed matter having good, clear, and high-quality images. On the other hand, in the case of using a printing plate outside the present invention, good printed matter could not be obtained. In particular, in a printing plate in which a toner avalanche phenomenon occurred, a shadow portion of a halftone dot was crushed, and only an unsuitable copy was obtained. Example 3 To 44 g of the emulsion obtained in Example 1, 1 g of Sumikarone Navy Blue and 5 g of butanol were added, and the mixture was shaken with glass beads for 30 minutes using a paint conditioner.
Liquid developer I was prepared by dispersing the total amount of the resulting blue dispersion and the respective amounts of diisobutylene-octadecyl halfamide copolymer shown in Table 4 in an IP solvent to make the total amount 8 L.
~ V. Table 4 also shows the results of measuring the electrodeposition potential of each liquid developer in exactly the same manner as in Example 1. Using these liquid developers, plate-making processes such as reversal development, fixing, and elution were performed according to Example 1. As a result, those using the liquid developers I to III became printing plates of good images, and provided good printed matter. was gotten. But liquid developer IV,
In the case of using V, the toner avalanche phenomenon occurs at the time of reversal development, and the reproducibility is reduced in the halftone dot shadow area by the liquid developers I to II.
It was much worse than the printing plate obtained using I, and a good printed matter could not be obtained. Example 4 20 g of styrene-butyl methacrylate-N, N dibutylethyl methacrylate copolymer, carbon black # 30
5 g (manufactured by Mitsubishi Kasei) and 75 g of xylene were mixed and dispersed by an attritor using an iron ball for 3 hours. The total amount of the obtained black dispersion and each amount of cobalt naphthenate shown in Table 5 were dispersed in an IP solvent to make the total amount 8 L, thereby obtaining liquid developers VI to X. The electrodeposition potential of each liquid developer thus obtained was measured in the same manner as in Example 1. Table 5 shows the results. According to Example 1, the plate making process of reversal development, fixing and elution was performed using these liquid developers to obtain a printing plate. The printing plates developed using the liquid developers VI to VIII were all high-resolution printing plates with good resolution, and good-quality printed matter was obtained. However, the printing plate developed using the liquid developers IX and X has a toner avalanche phenomenon, particularly the shadows of the halftone dots are crushed, and a good printing plate cannot be obtained. In addition, the resolution was poor, and the image was of low quality with no gradation at the halftone dot portion.

According to the present invention, a halftone dot image having a high linear density can be developed at a high resolution without causing a toner avalanche phenomenon in an electrophotographic lithographic printing plate in an electrophotographic wet reversal developing process.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an electrodeposition potential measuring device used in the present invention. 11 ... glass cell, 12 ... electrode (-pole), 13 ... electrode (+ pole), 14 ... high voltage supply device, 15 ... surface voltmeter, 15a ... surface voltmeter probe, 16 ... ... Liquid developer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-49895 (JP, A) JP-A-55-105254 (JP, A) JP-A-63-163384 (JP, A) JP-A 63-163384 173075 (JP, A) JP-A-63-179368 (JP, A) JP-A-1-261660 (JP, A) JP-A-2-24680 (JP, A) JP-A-2-5755 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 13/28 G03G 13/10 G03G 9/12

Claims (1)

(57) [Claims] An electrostatic latent image corresponding to an image by uniformly charging the surface of an organic photoreceptor obtained by binding an organic photoconductive compound on a conductive support with a resin material and exposing the light image. Is formed on the surface of the organic photoreceptor, and a plate is produced by reversing the electrostatic latent image using an electrophotographic liquid developer containing charged toner particles. In the method for producing an electrophotographic lithographic printing plate, the electrodeposition potential as a liquid developer is 0 to 80 V as an absolute value.
Wherein the reversal development is carried out using an electrophotographic liquid developer set in the range of 1.